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Creating Soft Robotics with a Sewing Machine

New stretchable technologies and soft robotics being explored by engineers at Purdue University, West Lafayette, IN, could lead to innovations such as robots with human-like sensory skin and synthetic muscles, as well as wearable electronics. But to do so, they say, you would need a low-cost, highly stretchable electrical conductor to interconnect sensors and other components.

The Purdue team used a standard sewing machine to create ultra-stretchable interconnects made out of conventional wire sewn in a zigzag pattern and embedded in a rubbery, stretchable elastomer. They demonstrated that their “interconnect” can stretch 500 percent of its length, which could allow for new applications.

The researchers used their technique to demonstrate a highly stretchable “inductive strain sensor” to monitor the expansion of an inflatable urinary catheter balloon. Such an elastic technology could have applications in stretchable garments that people might wear to interact with computers or for therapeutic purposes. 

Since it was not practical to sew the wire directly into the rubbery elastomer, the researchers developed a technique to first sew the wire into a sheet of polyethylene terephthalate (PET) with a water-soluble thread. Then the rubbery stretchable polymer was poured over the sheet, encasing the wire as it solidified. Warm water was used to dissolve the thread, and the flexible polymer was separated from the PET sheet with the wire embedded in it.

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